The resonant acoustic frequency of a system is the natural free oscillation frequency of the system. A resonant acoustic system can be excited by a weak mechanical or acoustic driving force in a narrow band of frequencies, close or equal to the resonant frequency thereby inducing acoustic resonance in a targeted structure.
Acoustic resonance has been used to determine various properties of solid materials. For instance, Migliori et al in U.S. Pat. Nos. 4,976,148 and 5,062,296 and 5,355,731 disclose a method for characterizing a unique resonant frequency spectroscopic signature for objects derived from ultrasonic excitation of objects, the use of resonant ultrasound spectroscopy for grading production quantities of spherical objects such as roller balls for bearings, and the use of resonant ultrasound spectroscopy with a rectangular parallelpiped sample of a high dissipation material to enable low amplitude resonance to be detected for use in calculating the elastic constants of the high dissipation sample. However, the Migliori patents are directed to solid materials and not to selectively targeting organic or biologic material especially when liquid systems are involved.
In addition to interacting with inanimate structures, acoustic energy also interacts with living, biologic organisms and structures. Acoustic energy has been used extensively in medicine and biology for imaging structures, by directing an acoustic wave at a biologic structure and analyzing the reflection pattern of the acoustic wave. Also, acoustic energy has been used in physical therapy medicine for delivering heat to targeted areas of injury or pain. However, all of the above applications depend on using acoustic energy that is non-selective for the specific targeted biologic structure, and as such, may affect more than just the targeted structure.
Vago, R E., U.S. Pat. Nos. 5,048,520 and 5,178,134 discloses ultrasonic treatment of animals for topical hygiene and antiviral effects. The frequencies disclosed are in the range of 15 kilohertz to 500 kilohertz. They also report that non-enveloped viruses were refractive to the inactivating effects of the ultrasound. The mechanism cited for their antimicrobial effects is “cavitation” on the skin surface only, and they specifically avoid the use of resonant frequencies in their apparatus.
Moasser, M., U.S. Pat. No. 4,646,725 discloses the use of an adaptor for diagnostic ultrasound machines for treatment of skin and mucous membrane lesions caused by infectious agents including herpes virus. The method of treatment was 2.0 to 3.0 minutes at a power output of 1.5 watts per square centimeter, with no specific frequencies being cited. The use of acoustic resonance is not discussed or contemplated.
Johnston, R G., U.S. Pat. No. 5,426,977 discloses ultrasonic measurement of the acoustic resonances in eggs to provide a technique for establishing the presence of Salmonella bacteria. Johnson characterizes the eggs and determines the difference between the egg with and without Salmonella bacteria. As such, this method does not detect the actual micro-organism, but instead characterizes the vibrational modes of an eggshell, which are modified by the physical presence of a bacteria.
The prior art has failed to suggest a satisfactory method or system for affecting functions of a biologic structure without also affecting near-by tissue. Furthermore, the prior art does not provide for a method that allows precise detection of biologic or inorganic structures using acoustic resonance to produce a signature with high signal to noise ratio, while producing little effect in nearby structures. Still further, use of non-resonant acoustic energy in the prior art affects targeted and non-targeted structures equally.